Lateral neuron-specific post translational regulation of circadian genes by Sarah in Drosophila

Abstract

To find out the novel genes related to circadian rhythm, we performed behavioral screening of EP line containing p element bearing the upstream activating sequence (UAS) inserted near the transcription start site of genes in the 3rd chromosome. These flies were crossed with transgenic flies expressing Gal4 under the control of circadian promoters to drive target gene expression. We found a circadian controlling gene, Sarah (Sra), a member of regulators of calcineurin (CN) which is Ca2+/Calmodulin-dependent phosphatase. To evaluate the function of Sra in circadian clock, we modified Sra expression in pacemaker neurons by RNAi knock down (KN). These mutants showed abnormal behavior and decreased rhythmicity. Similarly, SraKO also showed arrhythmic behavior. The expression level of main circadian clock protein such as Period (PER) and Timeless (TIM) was decreased in both KN and KO mutant. Particularly, the large lateral ventral neuron-specific degradation was observed. However, the expression level of mRNA was not changed. Since Sra acts on Cn, we also tested locomotor activity of CnKO. Flies with weakened activity of Cn exhibit lowered rhythmicity and reduced PER and TIM level.